Pneumatic horn



Feb. 24, 1942. N. F. LEWIS PNEUMATIC HORN Filed Oct. 22, 1940 INVENTOR NORMAN F. LEWIS m I ATTORNEY Patented Feb. 24, 1942 Norman F. Lewis, Wilkinsburg, Pa., assignor to The Westinghouse Air Brake, Company, Wilmen-ding, Pa.,* a corporation of Pennsylvania Application October '22, 1940, 'Serial No. 362,195 I (01. 116-142) 4 Claims;

This invention relates to horn devices of the type embodying a flexible diaphragm adapted to be vibrated at a rapid rate by variations in air pressure, to produce sound.

a In devices of this type the flexible diaphragm is usually subject on one face to atmospheric pressure and has at the opposite facea pressure chamber, and either the diaphragm ,ora valve associated therewith is arranged to alternately open and close communication between said chamber and a passage through the horn bell leading to the atmosphere.

When the pressure chamber is at atmospheric pressure, the valve associated with the diaphragm is usually closed thereby, but when, due to operation of any suitable valve device under the control of an operator, the pressure cham beris. connected to a source of fluidpressure which is of a degree different, from that of the atmosphere, and a sufficient difierential of fluid pressures is thereby created on the diaphragm, the diaphragm is operated to open said valve. The communication between the pressure chamber and source of fluid pressure is usually restricted with respect to the flow capacity of the communication connecting said chamber 7, with the atmosphere through the horn bell sothat when the latter is opened by the valve a sudden reduction in the differential of pressures on the diaphragm will'occur to permit the diaphragm to close the valve. The differential of fluid pressures on-the diaphragm is .then again created and asa result the valve is again opened,

, from the following more detailed description of This operation or vibration of the diaphragm V continues as long as the pressure chamber is connected with the source of fluid pressure and is at such a rapid rate as to produce a soun suitable for signal purposes. 7

Inhorn devices of the above type the pressure chamber is normally at atmospheric pressure .as above mentioned, and a certain period of timeis therefore required to obtain a change .in pressurein said chamber which is of sufiicient degree to cause the diaphragm to operate. This delay is mostly due to the restriction in the communication between the pressure chamber and the source of fluid pressure, but may also be influenced by the tendency of the diaphragm to crack open the valve before a sufficient differential of pressures is obtained on the diaphragm to effect the full opening of the valve, and, as will be apparent, any such partial opening of the valve will delay obtaining said differential through the restriction above"mentioned.

the invention.

In the accompanying drawing; Fig. 1 is a fragmentary cross-sectional view of a horn device embodying the invention; and Fig. 2 is a diagrammatic view of a control system embodying the horn device shown in Fig. 1.

The horn device shown in the drawing for illustrating one use of the invention, is preferably of the type usually employed on railway locomotives and which is adapted to be controlled by fluid at a pressure above atmospheric pressure from the usual supply carried on such locomotives.

In the drawing the reference numeral I indicates the body of the horn device which is provided with a suitable mounting bracket 2 and which has a passage 3 open at one end to a passage 4 provided in the small end of a horn bell, 5 which is secured to the body I. The opposite end of passage 3 terminates at an annular valve seat I provided in the body I. A flexible laminated diaphragm unit 8 is disposed in body 'I in coaxial relation with the valve seat 7 and is clamped adjacent its peripheral edge between an annular shoulder 8 provided on a member I which is secured in the body I and an annular shoulder II which is formed on a cover plate l2 secured to body l by bolts I3. The plane including the shoulder 9 is ofiset from the end of the valve seat I and the shoulder H is of less diameter than the shoulder 9 so that when the opposite side of which engages one side of the diaphragm unit 8, and extending through said valve, disk, and unit is a rivet I! which rigidly secures the parts together. The pressure chamber I4 is connected through a relatively restricted port It to a fluid pressure supply cavity l9 formed in the body I. The cavity [9 is in turn connected to a pipe 29 leading to any suitable source of fluid under pressure such as a reservoir 28 and is thus adapted to be constantly supplied with fluid at substantially the pressure in said reservoir.

At the opposite side of the diaphragm unit 8 is a control chamber 22 which is connected by a passage 23 to a control pipe 24. The pipe24 is adapted to be connected with a valve device 29 which will open said pipe to the atmosphere when it is desired to efiect operation of the'horn device. This valve device is adapted to normally close communication between the pipe 24 and atmosphere and may be of any desired'type and arranged for control by an operatorin --any desired manner. In the horn device the passage 23is connected to the fluid pressure supply cavity 19 through a passage 25 in which there is disposed a choke 26 having a restricted port 21.

In operation, let it be assumed that the reservoir 28 is charged with fluid under pressure, and that the valve device 29 is in its normal condition closing communication between the pipe 24 and atmosphere. Fluid under pressure from the reservoir 28 will then be supplied through thepipe 20 to cavity l9 in the horn device and from said cavity will equalize through the restricted port l8 into pressure chamber 14 and through the restricted port 21 in-choke plug 29 into the controlchamber 22 and ipe 24. With the-pressure chamber [4 and control chamber 22 thusoharged with fluid at the same pressures, such pressure in the chamber [4 acting on the backof valve [5 in conjunction with the force applied to said valve by deflection of the diaphragm unit 8 urges said valve into contact with the annular valve seat I to thereby close communication between the pressure chamber I4 and the outlet passage-3 1 leading to the horn bell 5. This is the condition which the parts of the horn device at all times will assume when not operating to produce a signal.

Now when it is desired to cause the horn device to operate to effect asignal, the operator actuates the valve device 29 to open the pipe 24 to the atmosphere through a communication having a flow capacity exceeding that of the restricted port 21 in choke 26. As .a result, the pressure of fluid in control chamber 22 is suddenly reduced to substantially that of the atmosphere. Full reservoir pressure is at this timeacting in the pressure chamber l4, and is thus promptly rendered efiective to move or deflect the diaphragm unit 8 in the direction of the left-hand to unseat the valve I5.

When the valve I5 is unseated the vent communication from chamber M to the passage 3 leading to the horn bell 5 is opened and this; communication has a flow capacity so exceeding that of the supply choke i8 that the pressure in said chamber is suddenly reduced into the horn bell to a sufficient degree for causing prompt reverse movement of the diaphragm unit 8 and consequent seating of the valve Hi. When the valve is thus reseated, the pressure of fluid in chamber I4 is again increased .by .the supply through the restricted .port I8 .to a degree suflicient for deflecting the diaphragm 8 in the direction of the left-hand for again unseating the valve [5. The pressure of fluid in chamber I4 is then again suddenly reduced to allow reseating of the valve l5. This cycle of operation, or vibration of the diaphragm unit 8, occurs at a sufliciently rapid rate to cause vibrations of the air column in passage 3 and thereby in passage 4 of the horn bell, which will produce an audible sound suitable for signaling purposes, and will continue as long as the control chamber 22 is maintained open to the atmosphere through the operators control valve device 29.

It will be noted that when the operators control valve device 29 is venting the pipe 24 there will be a constant leak of fluid under pressure from cavity 19 through port 2'! in choke 26 to said pipe, but such leakage is so restricted as to have no effect on operation of the horn device.

When the operator desires to terminate the signal, he allows the valve device 29 to close the vent from pipe 24 following which the supply of fluid under pressure through port 21 to passage 23 and thereby to pipe 24 and control chamber 22 in the horn device will increase the pressure in said chamber to equalization with that supplied to pressure chamber l4 and this permits the pressure of fluid in the pressure chamber M acting on the valve 15 to hold said valve in seating contact with the seat I.

The venting of fluid under pressure from chamber 22 to eiiect operation of the horn device may be effected at as rapid a rate as desired due to the fact that the flow capacity through the passage 23, pipe 24, and the operators valve device 29 need not be limited or restricted in any way since the operation of the horn device is entirely independent thereof. By this improved structure the pressure chamber M can always be normally charged with fluid at a .pressure sufficient to cause the horn device to promptly operate upon the sudden venting of fluid from the chamber 22, it therefore being apparent that the restriction l8 between cavity i 9 and pressure chamber 54 will in no way retard response of the horn device to operation of the operators valve device 29, as occurs in structures in which the pressure chamber 14 as well as the chamber at the opposite side of the diaphragm are both normally at atmospheric pressure and in which fluid under pressure has to be supplied to the chamber 14 through the restricted opening I8,for causing the horn device to operate.

The invention is associated with a horn device of the type adapted to be operatedby fluid at a pressure greater than atmospheric pressure, but it is equally applicable to horn devices adapted to be controlled by vacuum or pressure below that of the atmosphere, as will be readily apparent.

While only one embodiment of the invention has been shown and described in detail, it is not the intention to limit the scope to that embodiment or otherwise than by the terms of the appended claims.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A pneumatic horn device comprising a vi- .bratory diaphragm structure having at one side a pressure chamber in constant communication with a source of fluid under pressure through a relatively restricted opening and controlling a communication of greater flow capacity than said opening between said chamber and atmosphere, said diaphragm structure being operative by the differential between the pressures in said pressure chamber and atmospheric pressure acting on the opposite side of said diaphragm structure to open and close said communication for varying said differential to eiTect vibration of said diaphragm structure, and means controlling the pressure on said opposite side of said diaphragm structure and selectively operative to either subject said opposite side to atmospheric pressure for rendering said diaphragm structure operative or to a different pressure for holding said diaphragm structure in the position for closing said communication.

2. A pneumatic horn device comprising a vibratory diaphragm structure having at one side a control chamber adapted to communicate with the atmosphere and having at the opposite side a pressure chamber in constant communication with a source of fluid under pressure through a relatively restricted opening and controlling a communication of greater flow capacity than said opening between said pressure chamber and atmosphere, said diaphragm structure being uperative by the difierential between the pressures in said chambers when said control chamber is at atmospheric pressure to open and close said communication for varying said difierential to effect vibration of said diaphragm structure, and means operative to either open said control chamber to the atmosphere to provide for vibration of said diaphragm structure or to provide for charging of said control chamber with fluid under pressure from said source for holding said diaphragm structure in the position for closing said communication.

said pressure and control chambers to render said diaphragm structure operative to close said communication, and means for opening said control chamber to the atmosphere through a communication having a flow capacity such as to reduce the pressure in said control chamber substantially to that of theatmosphere, said diaphragm structure being operative by the differential between the pressures in said pressure chamber and substantial atmospheric pressure in said control chamber to open and close the communication controlled thereby for varying said differential to effect vibration of said diaphragm structure.

4. A pneumatic horn device comprising a body having a supply chamber constantly supplied with fluid under pressure, a vibratory diaphragm structure disposed in said body and having at one side a control chamber connected to and supplied with fluid under pressure from said supply chamber, said diaphragm structure having at the opposite side a pressure chamber in constant communication with said supply chamber through a relatively restricted opening, said diaphragm structure controlling a communication of greater flow capacity than said opening between said pressure chamber and atmosphere, means for venting fluid under pressure from said control chamber at a rate exceeding the rate of supply thereto to thereby subject said diaphragm structure to substantial atmospheric pressure in said control chamber, said diaphragm structure being operative when the pressure of fluid in said control chamber substantially equals that in said supply chamber to maintain the communication between said pressure chamber and the atmosphere closed and being operative by the differential of pressures in said control and pressure chambers when said control chamber is open to the atmosphere to alternately open and close the last named communication for varying said differential to efiect vibration of said diaphragm structure.

NORMAN F. LEWIS. 

